Clinical and laboratory times¶
Find out what a time in the clinical and lab tables marks (an event, its documentation, a rounding), using signatures the event leaves in the signals.
Studies¶
| Study | Date | Status | Summary |
|---|---|---|---|
| How the anesthesia end time was charted | 2026-10-18 | current | The charted anesthesia end time is a mixture of 4 ways of writing a clock time (ceiling_30min, ceiling_10min, ceiling_5min, clock_minute), modelled as an offset from a device time. |
| How the anesthesia start time was charted | 2026-10-18 | current | The charted anesthesia start time is a mixture of 5 ways of writing a clock time (nominal_0740, nominal_0730, nearest_10min, nearest_5min, clock_minute), modelled as an offset from a device time. |
| How the operation end time was charted | 2026-10-18 | current | The charted operation end time is a mixture of 4 ways of writing a clock time (floor_30min, floor_10min, floor_5min, clock_minute), modelled as an offset from a device time. |
| How the operation start time was charted | 2026-10-18 | current | The charted operation start time is a mixture of 3 ways of writing a clock time (nearest_10min, nearest_5min, clock_minute), modelled as an offset from a device time. |
| Admission, discharge and length of stay | 2026-10-13 | current | Admission and discharge are dates at 1-day resolution, so length of stay is a derived triangular distribution, and discharge days show a weekly pattern rather than rounding. |
| What the lab timestamp marks | 2026-10-13 | current | VitalDB's lab time is a per-specimen timestamp: not the draw, and not the result. Blood gases are stamped 3–12 minutes after the draw, central-lab panels about 8–24 minutes after it, and the result follows a turnaround the release does not record. |
| Charted-time clock reconstruction | 2026-10-13 | current | The absolute clock time of every event can be recovered from the admission date, which makes minute-of-hour distributions possible despite de-identification. |
| Bias in charted intervals | 2026-10-13 | current | Charted intervals are biased because each end is rounded with a different anchor, and their per-case uncertainty is large relative to short intervals. |
| Imputed times, conformance failures and exclusion rules | 2026-10-13 | current | About one in twelve op ends was set from the recording rather than charted, and a small set of times fail basic conformance checks; all are encoded as exclusion rules. |
| What lab timestamps mark | 2026-10-13 | superseded | Merged into "What the lab timestamp marks" on 18 October 2026; kept so old links still work. The original finding: central-lab timestamps most likely mark specimen receipt in the lab, about 10 minutes after the draw. |
| Recovering the time of day | 2026-10-12 | current | The release shifts every case to start at 2100-01-01 00:00 UTC, removing the date and the time of day. The time of day (Korean local time) can be recovered to the minute from the admission date and the seconds of the EMR times. |
| Anaesthesia record times are rounded up | 2026-10-12 | current | Anaesthesia start and end entered on a 5-minute mark sit 90–290 s later, against device markers, than entries typed to the minute. Rounding up to the next 5 minutes fits every one of 11 markers better than rounding to the nearest or down. |
| Arterial line accesses in the pressure waveform | 2026-10-11 | current | Flushes, zeroing and blood draws leave clear signatures in the arterial pressure. A detector finds them in the waveform alone (about one access per hour) and matches 77% of lab draws to an access within 15 minutes, against 26% for random times. |
Observations from these studies¶
| Observation | Status | Summary |
|---|---|---|
| Anaesthesia record times on 5-minute marks are rounded up | established | An anaesthesia start or end entered on a 5-minute mark was rounded up to it: the event happened in the 5 minutes before, and on average a little earlier still. Clear for anaesthesia end; for anaesthesia start the margin is small, and the value model (How the anesthesia start time was charted) prefers rounding to the nearest mark. |
| Arterial timing steps cluster at line events | established | About a quarter of the steps in ECG→arterial-pressure timing fall within a minute of a line access or a cuff occlusion, against 4.5% at random times. |
| Every case starts at 2100-01-01 00:00 UTC | established | The release shifts each case to the same start, removing the date and the time of day. Within a case all times keep their spacing. |
| Op end was filled in from the recording end in 537 cases | established | In 537 cases (8.4%) the op end is exactly 10 minutes before the end of the recording, so it was filled in rather than charted. These cases are concentrated in thoracic surgery and under sedation or spinal anaesthesia. |
| The EMR clock's offset cannot be separated from documentation lag | established | Both routes between the EMR clock and the recorder run through the case start, so any EMR clock offset cancels. Without a time from outside the release it is confounded with how late entries are made. |
| The blood pressure cuff often sits on the arterial line's arm | established | Many "lost pulse" events in the arterial pressure are an NIBP cuff inflating on the same arm: the pulse fades and pressure decays to 35–50 mmHg, then returns as the cuff cycle ends. |
| The lab time is neither the draw nor the result | established | VitalDB's lab timestamp marks the specimen (logged at the lab, or entered from a theatre analyser): minutes after the draw and before the result, whose time is not recorded. |
The approach¶
The idea. Anaesthesia record entries and laboratory results carry times made by other systems and by people. An event often leaves a trace in the signals (an arterial blood draw in the pressure trace, the start of anaesthesia in the BIS and ventilation), and comparing the two shows what the recorded time stands for.
What it gives. Rounding rules (5-minute entries rounded up), documentation lag, and what a lab timestamp marks (here, a per-specimen time minutes after the draw, not the result time).
How. Detect the signal-side event independently, match it to the table entry, and fit how the recorded time relates to it (nearest, floor, ceiling, plus a lag), with random times as the control.
Pitfalls. Both sides may be measured from the same origin (the case start), so an offset can cancel and look like agreement. Without a time from outside the release, a clock offset and a documentation lag cannot be told apart.
References¶
- Goodwin AJ, Eytan D, Dixon W, Goodfellow SD, Doherty Z, Greer RW, McEwan A, Tracy M, Laussen PC, Assadi A, et al. Timing errors and temporal uncertainty in clinical databases – a narrative review. Front Digit Health. 2022;4:932599. ↗
- Rietveld P. Rounding of arrival and departure times in travel surveys: an interpretation in terms of scheduled activities. J Transp Stat. 2002;5(1):71-81. ↗